The present invention relates to a photosensitive resin composition. More particularly, the invention relates to a photo-sensitive resin composition having high sensitivity and capable of exhibiting excellent heat resistance and adhesion to the substrate surface when used as a solder resist, etching resist or plating resist.
It is well known in the prior art that a photosensitive resin is used as a solder resist, etching resist or plating resist in the manufacturing process of printed circuit boards.
For example, Japanese Patent Kokai 60-208377 discloses a solder resist composition comprising a phenol novolac-type epoxy resin or cresol novolac-type epoxy resin having ethylenically unsaturated groups, photopolymerization initiator and amine-based curing agent for the epoxy resin. Further, Japanese Patent Kokai 58-199341 discloses a heat-resistant photosensitive resin composition comprising a diallyl phthalate prepolymer, photopolymerizable monomeric compound and photopolymerization initiator.
Though excellent in respect of the resistance against heat and chemicals, these prior art photosensitive resin compositions have a defect that the resist pattern formed of the composition can be developed only by using a specific organic solvent as the developer, which is sometimes very expensive, to cause a great economical disadvantage.
It is a trend in recent years from the standpoint of prevention of environmental pollution and adverse influences on the workers' health to abolish use of chlorine-containing organic solvents in particular so that the organic solvents usable in the development treatment of resist patterns are more and more limited.
With an object to overcome the above mentioned problems, development works are under way for a photosensitive resin composition developable by using water or an aqueous alkaline solution. Unfortunately, none of such water- or alkali-developable photosensitive resin compositions hitherto developed is satisfactory in practical applications due to the poor storage stability of the composition as well as poor resistance against heat and chemicals and adhesion to the substrate surface of the resist layer formed therefrom.
As a general problem of photosensitive resin compositions, the manufacturing cost of a practically useful resin composition is unavoidably high when the composition is formulated with a variety of ingredients while a photosensitive resin composition having high sensitivity and excellent heat resistance can be obtained only by formulating the composition with a number of ingredients each of which is expected to contribute in its own part to the performance of the resin composition.